A calorimetric calibration system includes a thermoelectric calibration heat pump device disposed between fluid supplying inlet and outlet pipes coupled to the waterload. The calibration heat pump device provides a controlled delta temperature to the fluid flowing through the pipes for providing a standard of reference for the calibration of calorimetric measurement systems relying on the conversion of RF or microwave energy to heat. The thermoelectric calibration heat pump device consumes a relatively low electrical power, is small in size, inexpensive to manufacture, and is safe to operate.